But Japanese companies see opportunity in an important industry in China's backyard: liquefied natural gas.

Facing of an excess of natural gas at home, Japanese firms are selling LNG overseas, and Japan is making an effort to shape the gas market in many emerging Asian countries.

In October, Japan's trade minister said the country will offer $10 billion in support to supply LNG or build gas infrastructure in Asia. That's a move that will "kill several birds with one stone," according to Jane Nakano, a senior fellow in the Energy and National Security Program at the Center for Strategic and International Studies.

Not only will the investment help Japan slash its stocks of LNG, but it will also boost its alliance with the United States, Nakano said in a recent podcast: The development of infrastructure for natural gas around the world will help drive demand for America's own exports.

Southeast Asia is a fierce battleground for energy firms, as Japanese companies, armed with vast experience in the LNG field, build new plants and infrastructure to supply the region.

Gas demand in those countries is growing rapidly, and despite China's attempts to dominate the region through wider economic power, Japan still has a competitive edge in the natural gas industry.

China is busy trying to meet LNG demands at home as it tries to cut the country's dependence on coal, according to Nicholas Browne, head of Asia gas and LNG at consultancy Wood Mackenzie.

From importer to exporter

Asia's second-largest economy has been a top importer of liquefied natural gas market after the shutdown of the country's nuclear power plants following the 2011 Fukushima disaster. Japan imported 70 million metric tons of LNG in 2010, but its imports hit about 84 million metric tons in 2017, according to Thomson Reuters data.

That growth rate is slowing as nuclear reactors restart, however, and it's also resulted in too much supply. Browne explained that Japanese companies tend to sign up for long-term contracts, because of the security they provide.

Despite the slowing changes in Japanese gas consumption, BMI Research nevertheless predicts gentle growth through 2022.